Process of recovering strontium, cesium, cerium and rare earth values from radioactive solutions



EXAMLE I A number of experiments were carried out using solutions of 1 MBAMBP in various solvents. The aqueous feed solution containing cesiumin a concentration of 0.001 M; it was about 1 M in sodium hydroxide andhad a pH value of about 13. The temperature of the solution was 25 C.;equal volumes of aqueous and organic solutions were contacted. Theresults, as distribution coefiicients for cesium, DC, (concentration inorganic extractzconcentration in aqueous raffinate), are listed in TableI.

Table l 1 M BAMBP diluted with: DC

AMSCO-D95 25 Nitrobenzene 19 Diiso'propylbenzene 100 Shell-23421.; 260

Soltrol170 245 These results show that aliphatic diluents bring aboutconsiderably improved cesium extraction as compared with thataccomplished with the aromatic diluents or the partly aromatic andpartly aliphatic Amsco-D95.

Carbon tetrachloride was also found to be a suitable solvent. mable andis ideally qualified for nuclear magnetic resonance work.

EXAMPLE II An aqueous 0.001 M cesium nitratesolution, having a pH valueof 5.1 and a temperature of 25 C., was used; two runs were carried outin each of which an aliquot of the feed solution was contacted forminutes with an equal volume of an extractant. In the first run theextractant consisted of an 0.5"M solution of BAMBP in Soltrol-170; acesium distribution coefiicient of 0.006 was obtained.

In the second run the same solvent was used, but it also containedD2EHPA in a concentration of 0.23 M. Thedistribution coefiicient in thisrun was 5.3. This shows the beneficial effect of D2EHPA on cesiumextraction.

EXAMPLE III Eight runs were carried out using an aqueous acidic wastesolution (pH=4.5) containing cesium and a Soltrol-170 solution 0.5 M inBAMBP and 0.1 M in different phosphates. One control test was runwithout any phosphate. Equal volumes of organic and aqueous solutionswere again contacted at C. for 15 minutes. The results are compiled inTable II.

Table II DC for Cs None 0.006 Bis (Z-ethylhexyl) phosphoric acid 6.8

Bis (Z-ethylhexyl) 2-ethylhexyl phosphonate 0.3

Monodiisooctyl acid orthophosphate 3.0

Monoisooctyl acid orthophosphate 3.2

Octylphenyl acid phosphate 1.73

Tri (2-ethylhexyl) phosphate 0.06

Bis (2-ethylhexyl) hydrogen phosphite 0.97

EXAMPLE IV It has the desirable feature of being nonfiam- Cir Table IIIDistribution Coefficients 0.5 \I BAMBP gEfl i pH=10.5 pH=4 Cesium CeriumStrontium It is obvious from the above results that there is a criticalDZEHPA concentration'for cesium extraction below and above which'theextraction is reduced so as to yield a distribution coefiicient ofbelow 1. For the pH value of 10.5 thiscritical concentration wasdetermined to be between 0.006 and 0.1 M, while for the pH value of 4 itwas between about 0.01 and 1 M. Cerium and strontium extractionincreased steadily with increasing DZEHPA content.

Therefore, if cesium is to be extracted alone, the DZEHPA concentrationis best held between 0.01 M and 0.05 M, while for the coextraction ofcesium, strontium, cerium and other rare'earths, the DZEHPAconcentration should best be between 0.2 and 0.4 M.

It 'is well to point out here that other lanthanide rare earths behaveanalogously to cerium and are coextracted under about the sameconditions as cerium.

EXAMPLE V A number of runs were carried out, all using as the extractanta Soltrol-170 solution 0.3 M in DZEHPA b'ut containing varyingquantities of BAMBP. The aqueous waste solution had a pH value of 4.Again equal volumes of organic and aqueous solutions were contacted at atemperature of 25 C. for 15 minutes. The distribution coefiicientsobtained-are summarized in Table IV.

Table IV Distribution Coefficients BAMBP, M

Na Cs Sr Ce 0 0i 0. 03 13. 23 12. 30 0. 04 '0. 03 ll. 35 11. 70 0 04 0.03 ll. 52 11. 0. 0i 0. 06 0. 49 12. 03 0. 0; 0.16 8. 24 12. 25 0. 0) 4.72 3. 07 7. 10 0. 06 16. 4 1.85 7. 40

These data show that sodium is not taken up to any substantial degree bythe extractant of the process of this invention, no matter what theBAMBP concentration is; this might be a function of the D2EHPA. Cesiumrequires a minimum concentration of 0.15 M for the BAMBP in a 0.3 Msolution of D2EHPA. Strontium and cerium values extracted very well,even with the lowest BAMBP concentration used, namely of 0.001 M. Thus,one way of isolating cesium is to extract the cerium and strontium firstwith a DZEHPA solution containing a low concentration of BAMBP and thento contact the aqueous phase with a DZEHPA solution containing a higherconcentration of BAMBP, whereby the cesium will be extracted.

The following example compares the various long-chain phenols as totheir extraction efficiency for sodium, strontium, cerium and cesium.

EXAMPLE VI A feed solution was used that had a pH value of 4 andcontained sodium, strontium, cerium and cesium in concentrations ofabout 0.001 M. The organic extractants were Soltrolsolutions, containingDZEHPA in 7 a concentration of 0.3 M and the respective phenol in aconcentration of 0.5 M. Equal volumes of organic and aqueous solutionswere contacted at 25 C. for 15 It is obvious from the above data thatsodium is not extracted, for practical purposes, by the solvents of thisinvention. All other cations were satisfactorily taken up by the variousphenol solutions. The poor cesium extraction obtained withp-dodecylphenyl cannot be explained; the low results might be due toexcessive water solubility of the extractant.

The effect of variations in the pH value on the extraction of cesium,cerium and strontium is shown in the next example.

EXAMPLE VII Aliquots of an aqueous nitric acid waste solution containingcesium, cerium and strontium values were contacted each with an equalvolume of a Sol'trol-l70 solution 0.5 M in BAMBP and 0.23 M in D2EHPA.The temperature again was 25 C. and the contact time 15 minutes. Theaqueous feed solutions had different pH values which had been obtainedby the addition of varying amounts of sodium hydroxide. The results forthe various pH values (after extraction) are given in Table VI.

higher pH values. Promethium, a typical lanthanide, extracts well at pHvalues between 2 and 4, while calcium prefers the organic phase at pHvalues of between 3, perhaps even 2, and about 7.

In the following example the effect of temperature changes on cesiumextraction is illustrated.

EXAMPLE VIII Aliquots of a cesium solution having a pH value of 4.5 wereextracted, at different'temperatures with a Soltrol- 170 solution 0.5 Min BAMBP and 0.3 M in DZEPHA. The ratio of organitxaqueous again was 1,and the contact time was 15 minutes. The results are summarized in TableVII.

Table VII C. DC for Cs The above shows the improved cesium extraction attemperatures below room temperature.

EXAMPLE IX A series of extraction studies were carried out at differentpH values to determine the respective acid concentrations suitable forstripping'the various values from the organic extractant.

For this purpose equal volumes of an organic solution (Soltrol-170, 0.5M in BAMBP and 0.3 M in DZEHPA); and an aqueous feed solution wereequilibrated for 15 minutes at 25 C. The aqueous feed solution containedcerium (0.004 M); calcium (0.0007 M); cesium (0.005 M); strontium(0.0035 M); and sodium hydroxide (0.035 M).

After phase separation, portions of the aqueous raffinate were thenregenerated as feed solution by adding radioactive trace concentrationsof cesium. promethium, strontium, cerium and calcium nitrates. The pHvalue Table V I Cesium Strontium Cerium Promethirun Calcium pH DC p11 1)C pI-I D C p11 D C pI'I D C Z. 75 0. 82 3. (S2 0. 78 3. 2. l 8. 92 3.

It will be noted that cesium extracted well at pH values between about 3and 12; additionalwork showed that the pH value can be as high as 14.The cerium extraction drops off sharply with increasing pH value.Therefore, if cerium extraction is intended, the pH value should not behigher than 5. Strontium extracts well also at of each portion wasvaried by adding nitric acid. This regenerated portion was againcontacted with an aliquot of the above-specified organic extractant, andthe distribution coefiicient was determined as described above.

The results are summarized in Table VIII; the pH values were alwaysmeasured after extraction.

Table VIII Strontium Cerium Calcium Prmnethium Cesium DC pII DC pI'I DCp II DC pII DC pH United States Patent O The invention described hereinwas made in the course of, or under, a contract with the United StatesAtomic Energy Commission.

This invention deals with the separation and recovery of radioactivefission products, in particular of strontium, cesium, cerium andlanthanide rare earth metal values as they are present, for instance, inwaste solutions obtained in the processing of nuclear fuel. Theinvention is particularly concerned with the simultaneous recovery of Csand the other fission products just listed. However, the process of thisinvention also lends itself well to the treatments of ore solutions andother solutions containing nonradioactive isotopes of the above-listedelements.

The isotopes Sr Cs Ge and those of many of the lanthanide rare earthmetals have a fairly long half- -life and emit concentratedradioactivity for a considerable period of time; this radioactivitygenerates heat. These facts make removal of such fission products fromthe waste solutions imperative prior to disposal of the latter.Separation of these isotopes is also desirable for the purpose ofrecovery, because they have many uses. Sr for instance, which has ahalf-life of 28 years and is a beta-emitter but does not give off gammarays, is used as the heat source of thermoelectric generators. Cs has ahalf-life of 30 years and is a gamma-emitter; it is valuable for foodsterilization, for the polymerization ofhydrocarbons, in radiotherapyand in radiography. Ce (half-life 285 days) is used as a gamma-emitterfor atomic batteries.

Strontium, calcium, barium and some of the lanthanide rare earthsincluding cerium have been extracted heretofore from waste solutionswith a solution of di-Z-ethylhexylphosphoric acid (DZEHPA) in kerosene.This process is the subject matter of the assignees copendingapplication S. N. 202,337, now Patent No. 3,154,500, issued October 27,1964 to George Jansen, Jr. et a1. Cesium is not extracted in saidprocess.

Another process uses long-chain phenols dissolved in aromatichydrocarbons, such as xylene or diisopropyl benzene, for the extractionof the fission products listed above. This process is the subject matterof the assignees copending application S. N. 225,936, now Patent No.3,179,- 503, issued April 20, 1965, to Donald E. Horner et al. Thephenols there do not extract cesium from the normally acidic wastesolutions, but the solutions have to be neutralized to a pH value of atleast 12 to accomplish cesium extraction.

This neutralization of the waste solutions for extraction withlong-chain phenols causes a considerable volume increase, a feature mostundesirable for the storage on disposal of the solutions. Also, a highpH value is unfavorable for solutions having a high iron content,because then complexing of the iron is impossible. In order to extractcesium as well as strontium, cerium and rare earths from waste solutionsby the above processes, two extraction steps and thus two units, havebeen necessary, one for the extraction of strontium, cerium and rareearth-s with DZEHPA and one for the subsequent extraction of cesium withphenol in an aromatic diluent, after alkalinization of the solution.This makes for a rather complicated and expensive process. Also, in theextraction with DZEHPA dissolved in an aromatic the addition of tributylphosphate is necessary to prevent the formation of a third phase.

It is an object of this invention to provide a process for theprocessing of nuclear fuel waste solutions by which strontium, cesium,cerium and rare earths are extracted simultaneously in one step.

It is another object of this invention to provide a process for theextraction of cesium from nuclear fuel waste solutions which can becarried out from acidic as well as alkaline waste solutions.

It is still another object of this invention to recover cesium, cerium,strontium and lathanide rare earth metal values from aqueous wastesolutions that can be applied to the solutions as they are obtained bysolvent extraction of dissolver solutions of nuclear fuel.

It is also an object of this invention to provide a process for theextraction of nuclear fuel wastesolutions in which no, or very little,sodium hydroxide is necessary for pH adjustment, so that a comparativelysmall volume of solution needs to be processed.

It is still another object of this invention to provide a process forthe extraction of nuclear fuel waste solutions in which the addition ofa suppressor for the formation of a third phase, such ,as the additionof tributyl phosphate, is not necessary.

It is furthermore an object of this invention to provide a process forthe extraction of nuclear fuel waste solutions with a diluent solutionof an extractant which uses comparatively inexpensive diluent-s.

It isfinally also an object of this invention to provide a process forthe recovery of cesium, cerium, strontium and/ or lanthanide rare earthmetal values from ore solutions, brines, etc. for which pH adjustment isnot necessary.

It has been found that long-chain phenols, such as 4-sec-butyl-2-(a-methylbenzyl) phenol (BAMBP), when dissolved in aliphatichydrocarbons, instead of the aromatic ones used in application S.N.202,337, extract cesium values to a higher degree than do the phenolswhen dissolved in aromatic diluents. Halogenated aliphatic hydrocarbonsalso have this improved efifect. This will be illustrated later inExample I. It has also been found that, although BAMBP alone extractscesium only at pH values of above 12, and although DZEl-IPA does notextract cesium at all, a mixture of DZEHPA with the phenols, due to someunknown synergistic effect, extracts cesium to a high degree at any pHvalue within the range of from 3 to 14. The beneficial effect of DZEHPAwill be demonstrated later in Example 11. The extraction of cerium andstrontium decreases sharply with pH values increasing beyond 5 so thatfor coextraction of cesium with cerium and strontium the pH value isbest maintained at between 3 and 5.- These findings have been utilizedin devising the processes of this invention.

One embodiment of this invention thus comprises adjusting the pH valueof an aqueous cesium-containing waste solution to between 3 and 14,contacting the waste solution with a long-chain phenol and anorgano-phosphorus compound dissolved in an aliphatic hydrocarbon orhalogenated aliphatic hydrocarbon, whereby the cesium values are takenup by said phenol solution, and separating said phenol solution from theaqueous waste solution. The invention also comprises the process ofadjusting the pH value of an aqueous waste solution containingstrontium, cesium, cerium and lanthanide rare earths values to between 3and 5, contacting the aqueous solution with an organic solution of along-chain phenol plus di-2-ethylhexylphosphoric acid in an aliphatic orhalogenated aliphatic hydrocarbon diluent, whereby said strontium,cesium, cerium and rare earth values are taken up by said aliphaticsolution, and separating the aliphatic solution from the aqueous wastesolution.

All aqueous mineral acid solutions are suitable for the process of thisinvention; most of the waste solutions obtained from solvent extractionprocesses for which this invention is primarily intended are nitric acidsolutions. If the feed solutions contain iron, chromium, nickel and/oraluminum values, these cations should be complexed to make themsolvent-nonextractable; citrate-, HEDTA- or tartrate-anions containingcompounds are suitable for this purpose.

Di-Z-ethylhexylphosphoric acid is the preferred alkyl phosphoric acid.However, other related compounds such as his (2-ethylhexyl) phosphoricacid, monodiisooctyl acid orthophosphate, monoisooctyl acidorthophosphate and octylphenyl acid phosphate have given satisfactoryresults as will be shown in Example III.

The concentration of these alkyl phosphoric acids was found to becritical, as will be shown later in Example IV. It will be demonstratedthat for cesium extraction the D2EHPA concentration should be within therange of from 0.006 to 0.1 M when a BAMBP concentration of about 0.5 Mis used. It will also be obvious from said example that below and abovethis range practically no cesium extraction takes place when the pHvalue of the aqueous feed solution is 10.5. However, from an acidsolution having a pH value of 4, cesium extraction did take place up toa concentric of 1 M DZEHPA.

The phenols have to be those of a long-chain hydrocarbon, because thelower-chain phenols are not sufficiently water-immiscible.Water-immiscibility, of course, is necessary for phase separation afterextraction. Phenols found suitable are BAMBP, 4-tert-butyl-2-(a methylbenzyl) phenol (TerBAMBP), o-phenylphenol, p-dodecylphenol andp-chloro-o-benzylphenol. The effect of concentration changes of BAMBP ina kerosene-type hydrocarbon solution containing 0.3 M DZEHPA on cesium,strontium and cerium extractions will be shown in Example V.

The solvent yielding the best coextraction results for cerium, strontiumand cesium was a solution containing BAMBP and DZEHPA in a molar ratioof about 5:3. A ratio of approximately 5 yielded optimal results for theextraction of cesium alone in most instances. For the purpose of theinvestigations leading to this invention, a solution containing 0.5 MBAMBP and 0.3 M DZEHPA was found best.

The use of the long-chain phenols together with the alkyl phosphoricacids of this invention has an additional advantage. While with DZEHPAalone as the extractant the formation of a third phase occurs, whenwashed with a sodium carbonate solution according to the processes usedheretofore, and the addition of tributyl phosphate was necessary for thesuppression of that third phase BAMBP was found to have a similar effectas tributyl phosphate; no third phase occurs and tributyl phosphate neednot be added. The various distribution coefiicients obtained with someof the long-chain phenols intended for this invention are presented inExample VI.

A great number of aliphatic hydrocarbons and chlorinated aliphatichydrocarbons, if substantially water-immiscible, can be used as thediluent, or solvent, for the alkyl phosphoric acid and long-chainphenols. Soltrol- 170 was the preferred diluent; it is a paraflinichydrocarbon with the following typical boiling range: initial boilingpoint at 424 F.; 10% distilled at 429 F.; 20% at 432 F.; 50% at 437 F.;70% at 440 F.; at 448 F.; at 454 F.; and end point at 463 F.So'ltrol-l70 has a specific gravity, at 60 F., of 0.7728; a refractoryindex at 20 C. of 1.4315; a flash point at 760 mm. Hg. of 192 F. and afire point of 210 F. The flash and fire points were determined inaccordance with ASTM methods D56-52 and D92-52, respectively.

The pH value of the aqueous feed solution has an effect on theextraction of cesium, but a greater effect on the extraction ofstrontium, cerium and other lanthanide rare earths. It was found, asmentioned, that cesium can be extracted at a pH value within the rangeof from 3 to 14, but that the other fission products listed are onlysatisfactorily extracted within the pH range of from 3 to 5. Thereforethe pH value has to be adjusted according to the extraction intended,that is to between 3 and 5, if a coextraction of strontium andlanthanides with the cesium is to be brought about. The effect ofvarious pH values on the degree of extraction is illustrated in ExampleVII.

Room temperature is satisfactory for the process of his invention;however, it was found that cesium is extracted to a considerably higherdegree if the feed as well as the extractant solution are cooled toabout 10 C. This will be illustrated in Example VIII. On the other hand,cerium extraction is improved with increasing temperature. Therefore forcoextraction of cesium plus cerium, a compromise temperature of about 35C. is best, while for cesium extraction alone a temperature of about 10C. is preferred.

The ratio of organic and aqueous solutions may vary widely. A ratio offrom 10:1 to 1:10 for organic2aqueous is suitable, but equal volumeswere usually found best. Extraction can be carried out in a batchprocess or in a continuous column operation.

After extraction the phases are separated from each other byconventional means. The fission product values can then 'beback-extracted from the organic solution by contact with aqueous mineralacid. Any mineral acid is suitable for this purpose as long as it doesnot bring about precipitation of the fission products. For instance,sulfuric acid is not operative for the back-extraction of strontium,because it forms water-insoluble strontium sulfate. If acid, forinstance nitric acid of a pH value of 3, is used for back-extraction,cesium and strontium are back-extracted together, while cerium remainsin the organic phase. The cerium can then be back-extracted with an acidhaving a pH of between 5 and 6 or below 1. Cesium and strontium can beseparated from each other thereafter by known methods, e.g. by passingthe strip solution containing these values over a cation exchange resin,as is known to those skilled in the art. Also, a simple NaHCO laOHaddition will split the cesium from the strontium by the precipitationof the latter. An additional solvent extraction using DZEHPA or tributylphosphate will extract the strontium away from the ceslum, as isdescribed in detail in assignees copending application S.N. 202,337,mentioned above.

Instead of first co-stripping strontium and cesium, strontium and ceriumcan be back-extracted together from the organic phase by contact with anacid having a pH value close to 7; and this will leave the cesium in theorganic phase. Cesium can then be back-extracted with an acid having apH value of about 3. Experiments showing the nonextractability and thusthe stripping with nitric acid of different pH values are summarized inExample IX.

In the following, the examples referred to in the preceding paragraphsare given to illustrate the conclusions summarized therein.

9 The above data and those of Table V show that the acid for strippingcesium should have a pH value of below about 2.5; that for strippingstrontium a pH of below 2; that for stripping calcium either a pH valueof below 1.5 or one of above 7; the acid for stripping promethium shouldhave a pH value of below 1 or one of above about 4; and the acid forstripping cerium should have a pH value of below 1 or above 5.

It will be understood that the invention is not to be limited to thedetails given herein but that it may be modified within the scope of theappended claims.

What is claimed is:

1. A process of coextracting strontium, cesium, cerium and otherlanthanide rate earth values from an aqueous solution containing suchvalues comprising: adjusting the pH of said solution to a value ofbetween 3 and 5; contacting said aqueous solution with a substantiallywaterimmiscible aliphatic hydrocarbon solution containing aWater-immiscible phenol selected from a group consisting of4-secrbutyl-2-(a methyl benzyl) phenol, o-phenylphenol, p-dodecylphenol,p-chloro-o-benzylphenol and 4- tert-butyl-Z-(a methyl benzyl) phenol anda water-immiscible alkyl phosphoric acid selected from a groupconsisting of bis(2-ethylhexyl) phosphoric acid, monodiisooctyl acidorthophosphate, monoisooctyl acid oithophosphate and octylphenyl acidphosphate; whereby strontium, cerium, cesium and lanthanide rare earthvalues are taken up by said aliphatic hydrocarbon solution; andseparating said aliphatic hydrocarbon solution from said aqueoussolution.

2. The process of claim 1 wherein the water-immiscible aliphatichydrocarbon is a kerosene fraction, the water-immiscible phenol is4-sec-butyl-2-(a methyl benzyl) phenol and the water-immiscible alkylphosphoric acid is di(2-ethylhexyl) phosphoric acid.

3. The process of claim 2 wherein the water-immisci- 10 ble aliphatichydrocarbon contains 0.15 to 1.0 M 4-secbutyl-Z-(a methyl benzyl) phenoland 0.05 to 1.0 M di(2- ethylhexyl) phosphoric acid.

4. The process of claim 3 wherein the di(2-ethylhexyl) phosphoric acidis present in a concentration of from 0.2 to 0.4 M.

5. The process of claim 4 wherein the aqueous solution is at a pH of 4and the 4-sec-butyl-2-(a methylhexyl) phenol is present in aconcentration of 0.5 M.

6. A process of separating cesium values from cerium and strontiumvalues present together in an aqueous nitric acid solution with a pH of4 comprising: contacting said aqueous solution with an aliphatichydrocarbon solution 0.3 M in di(2-ethylhexyl) phosphoric acid and notmore than 0. 01 M in 4-sec-butyl-2-(a methyl benzyl) phenol, wherebycerium and strontium are taken up by said hydrocarbon solution;separating said hydrocarbon solution from said aqueous solution; thencontacting said aqueous solution with a second hydrocarbon solution 0.3M in di(2-ethylhexyl) phosphoric acid and at least 0.15 M in4-sec-butyl-2-(u methyl benzyl) phenol, whereby cesium values areextracted; and separating said second hydrocarbon solution from saidaqueous solution.

References Cited by the Examiner UNITED STATES PATENTS 2,910,442 10/1959 Kaplan. 3,047,601 7/1962 Johnson 23-23 X 3,122,414 2/1964 Horner etal 23-312 X 3,154,500 10/1964 Jansen et a1. 252301.1 3,179,503 4/1965Horner et al 23--25 X OSCAR R. VERTIZ, Primary Examiner.

H. T. CARTER, Assistant Examiner.

1. A PROCESS OF COEXTRACTING STRONTIUM, CESIUM, CERIUM AND OTHERLANTHANIDE RATE EARTH VALUES FROM AN AQUEOUS SOLTION CONTAINING SUCHVALUES COMPRISING: ADJUSTING THE PH OF SAID SOLUTION TO A VALUE OFBETWEEN 3 AND 5; CONTACTING SAID AQUEOUS SOLUTIONWITH A SUBSTANTIALLYWATERIMMISCIBLE ALIPHATIC HYDROCARBON SOLUTION CONTAINING AWATER-IMMISCIBLE PHENOL SELECTED FROM A GROUP CONSISTING OF4-SEC-BUTYL-2-(A METHYL BENZYL) PHENOL, O-PHENYLPHENOL, P-DODECYLPHENOL,P-CHLORO-O-BENZYLAPHENOL AND 4TERT-BUTYL-2-(A METHYL BENZYL) PHENOL ANDA WATER-IMMISCIBLE ALKYL PHOSPHORIC ACID SELECTED FROM A GROUPCONSISTING OF BIS(2-ETHYLEHEXYL) PHOSPHORIC ACID, MONODIISOOCTYL ACIDORTHOPHOSPHATE, MONOISOOCTYL) ACID ORTHOPHOS-D PHATE AND OCTYLPHENYLACID PHOSPHATE; WHERBY STRONTIUM, CERIUM, CESIUM AND LANTHANIDE RAREEARTH VALUES ARE TAKEN UP BY SAID ALIPHATIC HYDROCARBON SOLUTION; ANDSEPARATING SAID ALIPHATIC HYDROCARBON SOLUTION FROM SAID AQUEOUSSOLUTION.
 6. A PROCESS OF SEPARATING CESIUM VALUES FROM CERIUM ANDSTRONTIUM VALES PRESENT TOGETHER IN AN AQUOEUS NITRIC ACID SOLUTION WITHA PH OF 4 COMPRISING: CONTACTING SAID AQUEOUS SOLUTIONK WITH A ALIPHATICHYDROCARBON SOLUTION 0.3 M IN DI(2-ETHYLHEXYL) PHOSPHORIC ACID AND NOTMORE THAN 0.01 M IN 4-SEC-BUTYL-2-(A EMTHYL BENZYL) PHENOL, WHEREBYCERIUM AND STRONTIUM ARE TAKEN UP BY SAID HYDROCARBON SOLUTION;SEPARATING SAID HYDROCARBON SOLUTION FROM SAID AQUEOUS SOLUTION; THENCONTACTING SAID AQUOUS SOLUTION WITH A SECOND HYDROCARBON SOLUTION 0.3 MIN DI(2-ETHYLHEXYL) PHOSPHORIC ACID AND AT LEAST 0.15 M IN4-SEC-BUTYL-2-(A METHYL BENZYL) PHENOL, WHEREBY CESIUM VALUES AREEXTRACTED; AND SEPARATING SAID SECOND HYDROCARBON SOLUTION FROM SAIDAQUEOUS SOLUTION.